Oscillograph



Aug. 24, l193.7. .1. T. M. MALPICA OSCILLOGRAPH Filed June 17, 1936 3Sheets-Sheet l Figi.

EL? a r H Inventor: Jose' T Mlreles Malp|caby 7VZ Ag His Attorney.

Aug. 24, 1937. J. T. M. MALPlc OSC ILLOGRAPH 3 Sheets-Sheet 2 Filed June1'?, 1936 Inventor:

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Aug. 24, 1 T M MALPICA OSGILLOGRAPH Filed June 17, 1956 3 Sheets-Sheet 3ITM/emisor A Jose' T. Mreles Malpica/ by 751W 49M is Attorney.'

Patented Aug. 24, i537 oscILLoGaA'rn Jos T. Mreles Malpica, Schenectady,N. Y., assignor to General Electric Company, a corporation of New YorkApplication June 17, 1936, Serial No. 85,812

12 Claims.

My invention relates to recording apparatus and concerns particularlyoscillographs of the Wpc employing a deflectible beam of radiant energyto produce the record curve.

The principal object of my invention is to provide an arrangement forproducing with a cathode ray oscillograph clearly-visible andwell-defined permanent record curves of very rapidly varying phenomena,particularly phenomena which are very short in duration andncnrecurrent.

It is an object of my invention to provide an arrangement for causingthe deflections traced on a fluorescent screen to record directly upon asensitive lm instead of being photographed.

It is an object of my invention to provide a light concentrator forsensitive film oscillographs.

It is also an object of my invention to arrange a cathode rayoscillograph to make relatively long records.

Other and further objects and advantages will become apparent as thedescription proceeds.

For the observation of extremely high-speed phenomena, cathode rayOscilloscopes are known in which a beam of radiant energy, impinging ona uorescent screen to make the end of the beam visible, iselectrostatically or electromagnetically deflected along transverse axesto trace a curve on the fluorescent screen, which, by

persistence of vision. appears to the eye as a continuous curve. In thecase of regular wave forms of alternating quantities or in the case ofregularly recurring transients, a record of the phenomena may be made byphotographing the curve traced on the fluorescent screen as inphotographing any object. However, in the case of isolated transients,which cause the beam to trace the curve on the screen only once,insufilcient light is produced for photography. In carrying out myinvention in its preferred form, I do not photograph the fluorescentscreen with a camera in the ordinary way but I cause the light spots onthe screen to affect the photographic film directly by passing the filmas close as possible to the fluorescent screen in order to increase theeffect upon the film. In order to prevent either blurring of the film orcomplete loss of the image by diffusion of the light from the lightspots, I may provide a suitable condenser or light concentrator betweenthe wall of the cathode ray tube and the photographic film.

The invention will be understood more readily from the followingdetailed description when considered in connection with the accompanyingdrawings and those features of the invention which are believed to benovel and patentable will be pointed out in the claims appended hereto.In the drawings, Fig. 1 is an end elevation, partially in section, of afilm-driving mechanism for a cathode ray oscillograph embodying my in- 5vention, the cathode ray tube and a portion of the film being removed topresent a view' into the film-driving mechanism; Fig. 2 is aside'elevation, partially in section, of the mechanismof Fig. 1,together with the end portion of a cathode` 1C ray tube with alight-concentrating shield; Fig. 3

is a schematic diagram showing the beam deflection in a cathode rayoscillograph; Fig. 4 is a fragmentary enlarged sectional view of a. portion of the apparatus of Fig. 2 showing a section cut by a planeextending lengthwise through the light-concentrating shieldperpendicular to the plane of the paper in Fig. 2; Fig. 5 is anenlargement of a portion of Fig. 2 showing a section of the part of thelight shield immediately 2( surrounding the light concentrator; Fig. 6represents a modification of the apparatus of Fig. 5; Fig. 7 is a graphillustrating a form of curve which may be produced with the apparatus;Fig.

8 is a diagram showing a portion of the glass wall 25 of a cathode raytube and a fluorescent screen and explaining the diffusion of light froma point on the screen; Fig. 9 is another diagram showing graphically thediffusion and variation in strength of light emanating from a brightspot 3 on the screen; Fig. 10 is a graph illustrating the effect ofdiffusion in tracing a sine wave; Fig. 11

is a fragmentary sectional view (corresponding to Fig. 5) of a lightshield with the openings filled by quartz rods, the section cuttingplane 3 being parallel with the direction of travel of the film as inFigs. 2, 5, and 6 Fig. 12 is a fragmentary sectional view of a modifiedarrangement with lenses embedded in the end Wall of a cathode ray tube,the section cutting plane being per- 4 pendicular to the directiontravel of the film as in Fig. 4; Fig. 13 is a fragmentary sectional viewof a modified arrangement with quartz tubes inserted in the end wall ofthe cathode ray tube, the section cutting plane being perpendicular to 4the direction of travel of the film as in Figs. 4 and 12; Fig. 14 is afragmentary view of a modified light shield, locking toward the end ofthe cathode ray tube, for use with stationary instead n of moving films;Fig. 15 is a modification of the arrangement of Fig. 16 with afabricated structure and Fig. 16 is a` sectional view of a modifiedconstruction having a light shield integral with the end wall of a tube.Like reference characg ters are utilized in the drawings to designatelike parts throughout.

As is well known, cathode ray oscilloscope tubes are provided withsuitable arrangements for generating the rays and focusing them to forma narrow beam. Since my invention does not relate to these arrangements,they need not be illustrated or described. As illustrated in Fig. 3,such a tube I I is provided with suitable means, such as anelectromagnetic coil or a pair of electrostatic deflection plates I2,for deflecting a beam between two limits, such as I3 and I4. The endwall I5, which is usually circular, is made convex and lined with afluorescent screen I5 which produces a momentary spot of light at thepoints Where the cathode rays impinge. The deflection plates I2 alonedeflect the beam within arplane parallel to the paper and substantiallyintersecting the tube II in accordance with variations in a voltage tobe measured which is applied between the plates I2. For. providing atiming axis and deecting beam transversely. a second pair of defiectingplates I'I may be provided in Oscilloscopes in which a curve traced onthe fiuorescent screen I6 is to be viewed directly by the human eye.When the phenomenon observed is recurrent and retraces the same curveindefinitely, a record thereof may be obtained by photographing itsince, by continued exposure of the photographic film to the curve,enough light may be obtained to affect the film.

However, in accordance with my invention, since I desire to obtainrecords of nonrecurrent phenomena, the momentary traces of which on thefiuorescent screen cannot ordinarily be successfully photographed, Iplace a sensitized chart or film I8 against the end wall I5 having thefiuorescent screen I6. Instead of employing the deflection plates I'I toobtain a timing axis for the curve, I cause the film I8, itself, to bemoved in a direction perpendicular to the plane of the paper in Figs. 3and 4 and I permit the cathode ray beam to deflect only in a singleplane under the influence of the deflection plates I2.

In order to avoid fogging the film, I provide a shield I9 covering theentire end I5 of the tube II, except for openings in the plane ofdeflection I3-I4 of the cathode ray beam. For the sake of avoidingblurring or dimming of the record curve by diffusion of the light fromthe fluorescent screen I6, I provide a light concentrator in the form ofa row of perforations 20 in the shield I9. The perforations 20 havetheir axes perpendicular to the surfaces of the fluorescent screen I6,the tube end wall I5, and the shield I9, and all the axes lie within theplane of defiection I3-I4 of the cathode ray beam. If desired, an`insert 2I, shown enlarged in transverse section in Fig. 5, may beprovided in the shield I9 for carrying the openings 20. The insert 2| isof opaque material, the surfaces of the perforations 20 are blackened,and preferably the inner surface of the shield IS is also blackened tominimize stray light.

Since the shield I9 is provided with a row of perforations rather than acontinuous slit for the passage of the light rays affecting thesensitive film I8, any curve produced by the oscillograph will appear asa series of dots as illustrated in Fig. 7. This circumstance permits meto provide a convenient way for providing scale divisions on a plainfilm as the record is being produced. The perforations 20 are properlyspaced to product unit graduations and every tenth perforation is ofgreater diameter to produce larger light spots 22, representinggraduations in multiples of ten. Furthermore, the small perforations oneither side of the larger perforations are omitted to define a zero linethrough the larger light spots 23 separated from the rest of the curveby short gaps on either side of the zero line. If desired, either thelight spots 22 or 23 may also be made distinguishable by employingopenings of a different shape or character.

Any suitable means may be provided for causing the sensitive film I8 topass along the lightconcentrating shield I8. For example, the film maybe carried by two spools 24 and 25 (Figs. 1 and 2), being wound upon thespool 24 and unwound from the spool 25 by the motor 26, driving thespool 24 through suitable gearing 21. The spools 24 and 25 are suitablyiournaled within a lightproof box 28 wholly surrounding the end portionof the cathode ray tube I I. A strip spring 29 may be provided forkeeping the film I8 compactly rolled on the spools 24 and 25.

The accumulation of static charges by the film I8 is prevented byproviding a metallic shield 3l)v electrically connected to the metallichousing 28. A felt cushion 3| and phosphor bronze springs 32 serve tohold the film I8 closely but resiliently against the light-concentratingshield I9 over the perforation 20.

Fig. 8, showing in section, greatly`enlarged,. a portion of the tube endwall I5 and the fluorescent screen I6, illustrates the effect of theglass wall I5 in causing diffusion of the light emitted from a singlepoint 33 on the surface of the fluorescent screen I6 where the light hasbeen generated by a cathodgray impinging upon the screen I6. Owing torefraction of the light rays upon emergence from the glass wall I5,still greater diffusion takes place outside the wall I5 of the tube. Inactual practice, the deflecting beam of the cathode ray tube consists ofa bundle of cathode rays producing a light spot 34 of finite area on thefluorescent screen I6 (Fig. 9), and the area of this light spot becomesconsiderably enlarged upon emergence from the glass wall I5.

The curve 35 represents by its distance from the outer surface 35 of thewall I5 the relative intensity of light at various points on the surface36. At the surface 36, the light spot becomes progressively dimmertoward the edges, owing to greater deviation from normal of the lightrays.

In consequence, although a cathode ray beam may actually follow a sharpcurve, such as the curve 3l (Fig. 10) a light-sensitive film placedagainst the surface 36 (Fig. 9) would have a broadly and dimlyilluminated band 38, becoming dimmer toward the edges, so that therecord curve actually recorded would be both indistinct and lackingdefiniteness of position. Such disadvantages are overcome, however, bythe interposition of my light-concentrating shield I9. Since theperforations 20 are all perpendicular or normal to the fluorescentscreen I6 and the perforations are of appreciable length relative totheir diameters, only the relatively powerful normally energizing raysare permitted to strike the lm I8 and a distinct definite curve isproduced as illustrated in Fig. 7. The perforations 20 provide lightpaths perpendicular to the screen I6 and so transmit only effectivelight rays perpendicular to the screen I6 and the end wall of the tube.

For the sake of illustration, I have described my invention inconnection with cathode ray tubes producing electron emissions impingingupon a fiuorescent screen to generate light and other rays, such asactinic rays, to which a photographic type of lm is sensitive. It willbe understood, however, that my invention is not limited to this precisearrangement and obviously includes'tubes producing other types ofradiant energythan cathode rays as well as such tubes 5 or other typesof oscillographs in which no uorescent screen is used and the radiationfalls directly upon a suitable sensitive chart or film.

I have also obtained successful records employing a relatively thinperforated shield but l obviously greater 'curve sharpness is obtainablewith the relatively thick shield I9 since any danger of divergent lightrays passing through the shield is eliminated. As an alternative to thearrangement hereinbefore described and illusl trated in detail in Fig.5, under certain circumstances in order to obtain increased brilliancy.I may employ a light shield having a row of conical openings 39 (asillustrated in Fig. 6) with polished internal walls, the smallerdiameter ends 40 of the openings being toward the lm. Such openingsserve as reflecting condensers, being substantially equivalent to verydeep parabolic mirrors with their apices cut off.

If desired, cylindrical rods of quartz 4I or other material having ahigh transmission and suitable index of refraction may be tted into theopenings 20 of the arrangement of Figs. 2, 4, and 5 to serve as lightcondensers as illustrated in Fig. 11. The rods 4I may be inserteddirectly in the shield I9 instead of employing the insert 2 I Condensinglenses 42 might, of course, also be employed, preferably embedded in thesurface of the glass wall I5 as illustrated in Fig. 12. By embedding thequartz rods 4I in the glass wall I5, as shown in Fig. 13, a directnon-diffusing path would be provided for the light rays emanat# ing fromthe fluorescent screen IS.

In case the oscillograph is to be operated with a stationary sensitivefilm and the timing and measuring axes are obtained by deflecting thebeam along transverse paths, the entire working portion of the shield I9is provided with perforations 2D or with some other form of lighttransmitting paths perpendicular to its surface. To 45 permit puttingthe perforations as close together as possible, they may be staggeredWith centers at the intersection of GO-degree lines as shown in Fig. 14,which represents a fragment of an end view of a modied form of shieldI9.

If desired the effective spacing between the light transmitting paths inthe shield I9' may be decreased by utilizing hexagonal openings orhexagonal-prism light transmitters placed immediately adjacent asillustrated in Fig. 15. Fig.

55 15 is a fragmentary end view of the shield I9 magnified to show morein detail that light transmitting openings 42 are formed by joiningopaque sheet material to produce hexagonal-prismshaped spaces. Suchspaces may, if desired, be lled with a suitable light transmittingsubstance such as a transparent resin which may be melted and pouredinto the openings and then allowed to cool and harden. A suitablebacking plate will, of course, be temporarily used to prevent the liquidfrom running out of the openings.

' Among the resins which may be used for this purpose are a syntheticresin manufactured by Rohm & Haas Co., Inc., under the trade namePlexiglass and a resin manufactured by the Du Pont de Nemours Co. underthe trade na-rne ,Pontalite which I believe to be polymeric esters,largely polymethyl methacrylate. In using such material the liquidmonomer, methyl methacrylate may be poured into the openings 42 5 andthen polymerized and solidified by heat. I

understand methyl methacrylate to have this formula:

In case the openings 42 are lled, the shield I9' may form a part of theend wall I5 of the tube II and the iiuorescent screen I6 may form acoating on the back of the shield I9'. It will be understood that theshield will be suitably sealed to the remainder of the tube II to forman air-tight envelope as illustrated in Fig. 16.

Instead of lling up the openings in a grid such as shown in Fig. 15, thelight shield may be made up by cementing together hexagonal prisms ofglass, quartz, transparent resin or other suitable substance to producea formation such as that appearing in Fig. 15. The side surfaces of theprisms may be sandblasted, etched or otherwise made opaque or an opaquecement may be employed for joining the prisms.

For slow-speed oscillegraphy, the fluorescent screen may be composed ofzink silicate but, for high-speed work in order to avoid leaving a bluron the rapidly traveling iilm, I prefer to use a material such ascalcium tungstate which is fast acting and does not leave an afterglow.

I have herein shown and particularly described certain embodiments of myinvention and certain methods of operation embraced therein for thepurpose of explaining its principle and showing its application but itWill be obvious to those skilled in the art that many modications andvariations are possible and I aim, therefore, to cover all suchmodifications and variations as fall within the scope of my inventionwhich is defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

l. A cathode ray oscillograph comprising an evacuated envelope with auorescent screen on a wall of said envelope, means for deiiecting acathode ray along a path across said screen in accordance withvariations in a measured quantity, a sensitized chart, means for passingsaid chart along said iiuorescent screen transverse to the path ofdeection of the cathode ray, a relatively thick opaque shield interposedbetween said iiuorescent screen and said chart with a row of openingseach perpendicular to said screen, and in the path of the cathode ray,and means for shielding said chart from any actinic rays exc'ept such aspass through said openings in said shield.

2. An oscillograph comprising in combination, a fluorescent screen,means for deflecting a beam of radiant energy across said screen inaccordance with variations in a measured quantity, a sensitized chart,means for passing said chart along said iluorescent screen, and arelatively thick opaque shield interposed between said uorescent screenand said chart with a row of openings, each perpendicular to saidscreen.

3.- An oscillograph comprising in combination, a uorescent screen, meansfor deflecting a beam of radiant energy across said screen, a sensitizedchart, means for passing said chart along said fluorescent screen, andan opaque shield interposed between said fluorescent screen and saidchart, said screen having a row of openings in the line of motion ofsaid beam.

4. An oscillograph comprising in combination, means for producing a beamof radiant energy,

means for defiecting said beam substantially in chart parallel to itselfin a direction transverse to said plane, and an opaque shield adjacentsaid 5 chart interposed between said chart and said beam-producingmeans, said shield having a row /of openings therein with centers in theplane of deflection of said beam.

5. An oscillograph comprising in combination, means for producing a beamof radiant energy, means for deflectlng said beam substantially in aplane, a sensitized chart having a surface transverse to said plane,means for moving said chart parallel to itself in a direction transverseto said l5 plane, and an opaque shield adjacent said chart interposedbetween said chart and said beamproducing means, said shield having arow of openings therein with centers in the plane of deilection of saidbeam, said openings being placed at uniform spacings, and includingopenings diil'erentiated from the remaining openings and spaced atmultiples of the spacings of the remaining openings.

6. An oscillograph comprising in combination, a fluorescent screen,means for deiiecting a beam of radiant energy across said screen inaccordance with variations in a measured quantity, a sensitized chart,means for passing said chart along said fluorescent screen, and arelatively thick opaque shield interposed between said uorescent screenand said chart with a row of openings each perpendicular to said screen,said openings being conical with their smaller diameters toward saidchart and having their interiors polished.

7. An oscillograph comprising in combination, a fluorescent screen,means fordefiecting a beam of radiant energy across said screen inaccordance with variations in a measured quantity, a sensitized chartadjacent said screen and a relatively thick shield interposed betweensaid fluorescent screen and said chart with a plurality of openingstherein perpendicular to said screen.

8. An oscillograph comprising in combination,

a fluorescent screen, means for deiiecting a beam of radiant energyacross saidscreen in accordance with variations in a measured quantity,a

sensitized chart adjacent said screen and a rela# of radiant energyacross said screen in accordance with variations in a measured quantity,a sensitized chart adjacent said screen, and a member interposed betweensaid iiuorescent screen and said chart with a plurality oi lighttransmitting paths having boundaries for diverting light rays notperpendicular to said screen.

l0. An oscillograph comprising in combination a iiuorescent screen,means for deiiecting a beam of radiant energy across said screen inaccordance with variations in a measured quantity, a sensitized chartadjacent said screen, and a member interposed between said fiuorescentscreen and said chart with a plurality of lightconcentrating devicesproviding light transmitting paths perpendicular to said screen.

11. An oscillograph comprising in combination a fluorescent screen,means for deilecting a beam of radiant energy across said screen inaccordance with variations in a measured quantity, a sensitized chartadjacent said screen, and a member interposed between said iluorescent'screen and said chart with a plurality of quartz rods thereinperpendicular to said screen.

12. In a radiant-energy-beam oscillograph, means for producing aradiant-energy-beam deflectible within a plane, and alight-concentrating shield for the oscillograph comprising an opaqueplate adapted to cover the beam-receiving end of the oscillograph andhaving a row of openings therein with axes within said plane andperpendicular to said plate.

JOSE T. MIRELES MALPICA.

